The present invention relates to a magnetic/adsorbent material composition, and more specifically to a magnetic/adsorbent material composition that uses different types of adsorbent material bonded to magnetic materials to adsorb and then remove the molecules adsorbed from a fluid or gas.
Molecular sieves are porous, synthetic, crystalline alumino-silicates that function to adsorb some molecules and reject others. The adsorption and desorption are completely reversible. These molecular sieves are adsorbents and referred to in the industry as zeolites. Other adsorbents exist, such as carbon fiber, carbon foam, silica gel, and activated alumina, and each has a unique application. Zeolite molecular sieves have a high kinetic rate of adsorption and have over 50 species that perform differently. The wide range of molecular sieve custom choices make zeolites a desirable material for many applications. Zeolite properties of ion exchange, reversible loss and gain of water, and the adsorption of other gases and vapor make zeolites useful adsorbents.
The molecular sieve crystal structure is a tetrahedron of four oxygen anions surrounding smaller silicon or aluminum cations. Sodium ions, calcium ions, or other exchangeable cations make up the positive-charge deficit in the alumina tetrahedral. Each oxygen anion is also shared with another silica or aluminum tetrahedron, extending the crystal lattice in three dimensions.
The crystal structure is honeycombed with relatively large cavities that are interconnected by apertures or pores. The entire volume of these cavities is available for adsorption. For example, the free aperture size of the sodium-bearing Type 4A molecular sieve (manufactured by UOP Inc. of Des Plaines Ill.) is 3.5 angstroms in diameter, which allows the passage of molecules with an effective diameter as large as 4 angstroms. Altering the size and position of the exchangeable cations can change the size. By replacing the sodium ions with calcium ions, for example, the effective aperture size can be increased to 4.2 angstroms. Using different or modified crystal structures can also change the aperture size.
Adsorbents are a versatile process tool in adsorption systems. They are usually used in multiple-bed molecular sieve systems common to large scale, commercial fluid purification units. These separate beds can be plumbed together. A common approach involves one onstream bed that is drying and/or purifying the fluid, and another that is regenerated by hot purge gas and then cooled. In regenerated beds, the beds are heated by convection or conduction. In carbon fiber monolith beds, electrical current can be applied across the fibers. As the adsorbent bed cools, the bed begins the process of adsorbing gas from the working fluid and starts the cycle over again. When an adsorbent bed is saturated with working gas fluid, the cycle is complete. The adsorbent vessel beds are then reheated and cooled to repeat the previous cycle.
In situations where an interrupted flow is acceptable, a single adsorption bed can be used. Then when the adsorption capacity of the bed is reached, the bed is taken off-line and regenerated for subsequent use. Molecular sieves are particularly useful in situations that require gas streams that are extremely dry. Molecular sieves can obtain water concentrations below 0.1 ppmw in a dynamic drying service over a wide range of operation conditions.
When co-adsorption of carrier stream molecules is a serious problem (e.g., in olefinic process streams) co-adsorption can be prevented by selecting a molecular sieve with a critical pore diameter small enough to prevent other stream components from being admitted to the active inner surface of the adsorption cavities. Molecular sieves can also be used for one-step drying and purification by selecting the proper molecular sieve and providing sufficient bed to retain the other impurities along with water.
Since molecular sieves adsorb materials through physical forces rather than through chemical reaction, they retain their original chemical state when the adsorbed molecular is desorbed. There are five types of adsorption/desorption cycles:
1. Thermal swing cycles involving rising desorption temperatures;
2. Pressure or vacuums swing cycles involving decreased desorption pressures;
3. Purge-gas stripping cycles using a non-adsorbed purge gas;
4. Displacement cycles using an adsorbable purge to displace the adsorbed material; and
5. Absorptive heat recovery, using the retained heat of adsorption to desorb certain molecules (e.g., water).
Molecular sieves are available in a variety of shapes and sizes. The most common are: {fraction (1/16)} and xe2x85x9 inch pellets; beads, 8 by 12 and 4 by 12 mesh; three pellets bonded into a triangular type extrusion, granulated particles in sizes from 6 to 60 mesh; and powders. Zeolites in prior art are typically beads, cylindrical pellets, or solid molded shapes to prevent raw zeolite crystal powder from going into an airborne state when hot air is used for cooling. The raw zeolite crystal powder is approximately 3 to 5 microns in size and very difficult to handle. These pure crystals are mixed with a clay and binder like polyphenylene sulfide (PPS) or aluminum phosphate, to form the zeolite beads, pellets, and molds. Beads and pellets have an attrition rate that is predictable based on the type of liquid, gas, or vapor adsorbed, vibration, heating cycles, and hot air-drying velocity. Screen meshes are used to contain the beads and pellets and allow cleaning.
Zeolite has a large internal surface area (of up to 100 m2/g), and a crystal lattice with strong electrostatic fields. Adsorbates are the gases or fluids that zeolite adsorbents adsorb. Zeolite retains adsorbates by strong physical forces rather than by chemical adsorption. Thus, when the adsorbed molecule is desorbed by the application of heat or by displacement with another material, it leaves the crystal in the same chemical state as when it entered. The very strong adsorptive forces in zeolite are due primarily to the cations, which are exposed in the crystal lattice. These cations act as sites of strong localized positive charge, which electrostatically attract the negative end of polar molecules. The greater the dipole moment of the molecule, the more strongly it will be attracted and adsorbed. Polar molecules are generally those, which contain O, S, Cl, or N atoms and are asymmetrical. Water is one such molecule. Other molecules that adsorb include, but are not limited to Ar, Kr, Xe, O2, N2, n-pentane, neopentane, Benzene, Cyclohexane, and (C4H9)2N. Under the influence of the localized, strong positive charge on the cations, molecules can have dipoles induced in them. The polarized molecules are then adsorbed strongly due to the electrostatic attraction of the cations. The more unsaturated the molecule, the more polarizable it is and the more strongly it is adsorbed.
Carbon fiber and carbon foam monoliths (developed by Oak Ridge National Lab Tennessee, U.S.A.) reduce attrition and increase thermal efficiency, however these monoliths are still batch adsorptions like the pellets. These carbon fiber monoliths are more efficient to heat and do not require screens to contain the adsorption materials. Activated carbon fiber has a strong attraction to carbon dioxide and a surface area greater than 1000 m2/g. Carbon fibers can be activated for a wide range of molecules. Carbon foam has the highest thermal transfer rate, and gas or fluid can pass through it. Carbon foam can have additives applied, to make it an adsorbent and it can be atomized into smaller pieces.
A further drawback of current adsorbent batch systems is that the capacity of the adsorbent bed has to be matched to the volume of working substance. If the adsorbent capacity is too low, the adsorbent bed size has to be increased, or increased capacity can be gained by adding more beds. Further, adsorbents can become saturated while there is still working substance in presence of the bed, preventing the separated gas from being pure. This is inefficient because the adsorbent must be recharged more often than it would if each gas specific zeolite could be added to the air source and then removed from the gas source instantly after adsorption. If the adsorbent capacity needs to be high in a dense transportable system, the adsorbent vessel is larger than necessary and therefore unusable.
Desorption from zeolite powders shows no hysteresis. The adsorption and desorption are completely reversible. However, with pellet zeolite material some further adsorption may occur at pressures near the saturation vapor pressure, through condensation of liquid in the pellet voids external to the zeolite crystals. Hysteresis may occur on desorbing this macro-port adsorbent.
One drawback of the prior art (and devices described above) is that the zeolite is stationary in a bed, inherently requiring several vessels to separate several molecules in a batch process. Such zeolite gas separation systems inherently need to have several zeolite beds. Another drawback of the prior art devices described above, is that the zeolite beds have to be heated. The more adsorption capacity that is needed, the larger the bed and heated area have to become. Heat is lost in the high surface area of the bed vessel housing. Further, heat has to be applied to activate the bed. This heating in the presence of the working fluid can chemically change the working fluid. This increased surface area is inefficient. A small separate heated area is more desirable. There is a continuing need in the art for an adsorbent that can be separated rapidly from the source working fluid and then heated separately for desorption as well as cooled to prepare for the potential of adsorption, before it is reentered into the working gas or fluid.
A further drawback of the prior art, is that adsorbents do not float or suspend in a fluid in a controlled manner. It is desirable to have several types of controllable zeolite, one that floats on the surface of fluid or gas, one that suspends in solution, or gas, and one that sinks to the bottom of the adsorbent vessel.
Yet a further drawback of the prior art, is that the stationary adsorbent beds require that the working fluid be moved rather than the adsorbent. Remaining residue from the fluid, after adsorption, has to be moved from the bed. This fluid can be hazardous. It is desirable to remove the adsorbent from the residue so other chemical processing can occur in the residue without the adsorbent present. There is a continuing need in the art for the rapid removal of adsorbents, so that the volume and rate of the work can be increased. The present invention fulfills these needs and provides further related advantages.
The present invention is directed to molecular separators (magnetoadsorbents) that employ an adsorption material composition that uses magnetic fields to move adsorbent materials to different locations in a system requiring adsorbents. Magnetoadsorbents include soft magnetic materials (e.g., ferritic alloy metals) that are bonded to adsorbents such as zeolites, carbon fibers or foam, with binders that keep the active part of the adsorbents open for adsorption. Magnetic fields can attract the ferritic metals bonded to adsorbents. Different metals can be combined with different adsorbents with binders to provide different functions.
Magnetic characteristics of the magnetoadsorbents of the present invention are capable of adsorbing a selected molecule in a continuous process instantly separating a mixture of molecules. Magnetic fields are used to attract saturated adsorbents of magnetoadsorbents from a working substance in the solid phase as well as the liquid phase. The present invention provides a further improvement over the prior art because the amount of adsorbent material increases or decreases during processing and the location of the adsorbent can be moved from the adsorption vessel to the desorption vessel as part of the continuous process within the molecular sieve apparatus.
In another aspect of a preferred embodiment of the present invention, floating and suspending materials are added to the binders that bind the metals to the adsorbents. Many materials are satisfactory for this purpose that float, suspend or sink. Completely coating adsorbent materials and trapping air in the adsorbents provides floating adsorbents. Different air volumes are also trapped to make the adsorbent float or suspend.
In another embodiment of the present invention, the conduit between the first and second vessels contains a turbine. The turbine is coupled to a power transmission device outside the conduit such that when water diluted hydrogen peroxide is passed into an intake conduit it substantially separates the water from the hydrogen peroxide stream by water adsorption into a water adsorbent. The high concentration of hydrogen peroxide then passes through a catalyst bed that chemically changes the hydrogen peroxide into steam (of approximately 600xc2x0 C.) and oxygen. The heat in the steam regenerates the zeolite powder at the same time it rotates the rotor of the turbine generating power, which is transmitted to the power transmission device. The air stream containing zeolite dust, water vapor, and oxygen passes through an air stream reverse rotation moisture separator returning dry zeolite dust to the intake conduit and centrifugally collects the water into a separate drain. This process continuously recycles the magnetoadsorbent or an adsorbent dust alone.
In a further embodiment of the present invention, a separator device is connected in fluid communication with the conduit of a fuel cell that convert hydrogen and oxygen to water generating electricity. The zeolite powder will be passed in the air stream to deliver oxygen and hydrogen to the cell membrane and then remove the water from the wastewater side of the fuel cell. Three species of adsorbents can be applied in the magnetoadsorbent, each can be contained within a closed loop of their own to deliver and adsorb each the above molecules.
In yet a further embodiment of the present invention, the first vessel and separator device are coupled to a hydrogen-oxygen fuel cell. The adsorbent material in the first vessel draws water from the fuel cell, thereby cooling the cell and improving the fuel cell efficiency. The separator device may be used to remove a portion of the water passing out of the fuel cell to delay the point at which the first vessel must be desorbed.
In yet a further embodiment of the present invention, the adsorption has previously been employed to separate molecules from a mixture of molecules. Adsorption is a process that utilizes the natural affinity certain adsorbent materials have for adsorbates. A typical adsorption cycle employing adsorption includes two phases. During one phase, the dried or charged adsorbent material is exposed to a liquid adsorbate. The affinity the adsorbent has for the adsorbate causes the adsorbate to enter a vapor state as it is attracted to the adsorbent. The conversion of the adsorbate from a liquid state to a vapor state is an endothermic reaction, which extracts heat from the environment surrounding the liquid, and therefore cools the environment and heats the adsorbent. During the second phase, additional heat is supplied to the adsorbent to expel or desorb the adsorbed vapor, thereby recharging the adsorbent. The desorbed vapor is condensed and cooled, and the two-phase cycle is repeated.
In another embodiment of the present invention, a separator device is connected in fluid communication with the conduit between the first and second vessels. The separator removes a part of the working substance, which passes from the second vessel to the first during adsorption. The part of the working substance removed by the separator may be returned to the second vessel for another cycle without requiring the first vessel to be heated. The separator device therefore delays the point at which the first vessel is heated to desorb the working substance.
In yet another embodiment of the present invention, the adsorbent material may include a carbon fiber material. Carbon fiber and carbon foam can be attached to magnetic alloys. Carbon materials like carbon foam mentioned above, for example, can be foamed with magnetic alloys in the foam. This carbon foam has a low-density highly conductive surface area making it one of the most thermally conductive materials. (Aluminum foam, copper foam, ceramic foam, etc. can be applied as well). Carbon foam magnetoadsorbents can be pulled in and out of fluids cooling the fluid. Carbon foam magnetoadsorbents are easier to obtain a thermal exchange with because they are broken down into movable small pieces that have high surface area exposure and can be applied to remove heat or distribute heat in air-conditioned and heating systems.
In still another embodiment of the present invention, carbon fiber monolith are injected with odorents and electrically desorbed to reproduce smells. These systems are applied to reproduce smells over the Internet and TV signals.